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Blue Shark
The Blue Shark is a medium-sized shark. The females grow 7 to over 10 feet (2.1 to 3 meters) long — as long as a recreational kayak — and weigh 200 to 400 pounds (91 to 181 kilograms), about as heavy as a calf. The males are 6 to 9 feet (1.8 to 2.7 meters) long and weigh 60 to 120 pounds (27 to 54 kilograms). The females are larger than the males because they have to be big enough to carry their babies. Also, females have three times’ thicker skin than males because the males tend to bite during the mating process. The largest blue shark ever caught was 12.6 feet (3.8 meters) long and weighed over 800 pounds (363 kilograms). Blue sharks are pelagic sharks, which means that they are found in open waters, neither near the ocean floor nor near the shore, often spotted just below the surface in deep waters. They are found all over the world, as far north as Norway and as far south as Chile, off the coasts of every continent except Antarctica. They prefer cool waters, though, below 68 degrees Fahrenheit (20 Celsius). They are often seen off the coasts of Wales, Canada, Japan and South Africa. Squid are important prey for blue sharks, but their diet includes other invertebrates, such as cuttlefish and pelagic octopuses, as well as lobster, shrimp, crab, a large number of bony fishes, small sharks, mammalian carrion and occasional sea birds. Whale and porpoise blubber and meat have been retrieved from the stomachs of captured specimens and they are known to take cod from trawl nets. Sharks have been observed and documented working together as a "pack" to herd prey into a concentrated group from which they can easily feed. Blue sharks may eat tuna, which have been observed taking advantage of the herding behaviour to opportunistically feed on escaping prey. The observed herding behaviour was undisturbed by different species of shark in the vicinity that normally would pursue the common prey. The blue shark can swim at fast speeds, allowing it to catch up with prey easily. Its triangular teeth allow it to easily catch hold of slippery prey. It is estimated that 10 to 20 million of these sharks are killed each year as a result of fishing. The meat is edible, but not widely sought after; it is consumed fresh, dried, smoked and salted and diverted for fishmeal. There is a report of high concentration of heavy metals (mercury and lead) in the edible flesh. The skin is used for leather, the fins for shark-fin soup and the liver for oil. Blue sharks are occasionally sought as game fish for their beauty and speed. Blue sharks rarely bite humans. From 1580 up until 2013, the blue shark was implicated in only 13 biting incidents, four of which ended fatally. Never seen a blue shark in an aquarium? Not to worry. The truth is that many sharks do not do well in an aquarium and the blue shark is among them. Even in spacious, circular tanks, the blue shark has only survived for as long as 7 months, dying because of stress or illness. Needless to say, you also can’t keep a blue shark for a pet.